WEDNESDAY, March 28 (HealthDay News) -- Deaths from cancer in the United States continue to decline, health officials report.

However, deaths from some types of cancers are on the increase and racial disparities remain in cancer deaths and diagnosis, according to the report from the U.S. Centers for Disease Control and Prevention.

"This annual report shows that a lot of the positive momentum we have seen in cancer control has continued," said report co-author Dr. Marcus Plescia, director of CDC's Division of Cancer Prevention and Control. "We are still seeing decreases in the incidence in death rates for many cancers and particularly for many of the most common cancers."

The focus of this report was obesity's impact on cancer. "That's important, because we don't think the public is aware of that," Plescia said.

For six cancers, there is good evidence of a relationship between obesity and cancer: esophageal, kidney, pancreatic, endometrial, colorectal and breast cancer, he noted.

In addition to the CDC, researchers from the North American Association of Central Cancer Registries, the U.S. National Cancer Institute and the American Cancer Society collaborated on the report, which was published online March 28 and will appear in the May print issue of the journal Cancer.

According to the report, the rate of new cancer diagnoses among men dropped an average of 0.6 percent per year between 2004 and 2008.

For women, the rate of cancer dropped 0.5 percent per year from 1998 to 2006, but has leveled off since 2006, the researchers found.

Most of the declines in cancer have been in lung, breast, colon and prostate cancer.

However, cancers of the esophagus, kidney, pancreas, liver and thyroid have been increasing, as well as endometrial cancer, the researchers found.

The increase in these cancers appears largely due to the increase in obesity, Plescia said. Lack of physical activity is also associated with these cancers, he noted.

In addition, melanoma rates are also increasing. The rise in incidence of this skin cancer appears due to continued sun exposure and the use of tanning beds, Plescia said.

The main reasons for the drop in lung cancer rates is mostly due to fewer people smoking, Plescia said.

For the second year in a row, deaths from lung cancer have dropped among women. Among men, the rate had continued to decline since the early 1990s, according to the report.

For other cancers such as colon, breast and prostate, the decreases in deaths is due to screening and better treatments, he said.

However, the rates for breast cancer have leveled off. "I am a little concerned about that, because we ought not to see this leveling off, because we can still be driving these rates down with more women getting screened," Plescia said.

Right now, about 70 percent of women are being screened, but Plescia said he would like to see that increase to at least 85 percent of women.

The screening rates for colon cancer are also still far too low, he added.

Cancer rates have increased among children -- 0.6 percent a year from 2004 to 2008. However, deaths rates from cancer among children dropped 1.3 percent a year in the same period, the researchers said.

Despite the improvements in many cancer rates, racial disparities continue to exist, the researchers found.

From 2004 to 2008, there were more cancers seen among black men and white women.

Deaths from cancer were highest among black men and black women. However, these groups also showed the biggest drops, compared to Asians and Hispanics, the researchers noted.

These differences may be due to differences in risk factors and access to screening and treatment, they suggest.

In addition, "there are studies that show if you are black, Hispanic or American Indian you're likely not to get as good care," Plescia said.

Ahmedin Jemal, vice president of surveillance research at the American Cancer Society, commented that "there is good news, but there are also some worrisome trends because some cancers are increasing, mostly those that are associated with obesity."

A combination of fewer smokers and improvements in cancer screening and treatment has been driving the decline in cancer rates and deaths for the most common cancers, he said.

But, to get the rates down for the cancers that are increasing, more money for research is needed, Jemal said.

People who want to lower their cancer risk should not smoke and maintain a healthy body weight through diet and being physically active, he added.

More information

To learn more about cancer, visit the American Cancer Society.